Check draft damper



c. B. ROGERS 2,033,388

CHECK DRAFT DAMPER v Filed Jan. 28, 1935 Patented Mar. 10, 1936 UNITED STATES PATENT OFFICE 2,033,398 CHECK DRAFT DAMPER Clarence B. Rogers, Seattle, Wash.

Application January 28, 1933, Serial No. 653,935

18 Claims. (01. 236-45) My invention relates in general to check draft Figure 3 is a sectional view of my device before dampers, and more particularly to such a damper it is installed. which is automatically opened under the influ- In the preferred form of my invention an inlet ence of an increased draft in the chimney flue conduit I is mounted on the upper side of a to admit air to such flue, which will reduce the pipe 2 which may be the flue pipe joining the draft to decrease the intensity of the fire in the furnace 3 and the stack 4, or may be a separate furnace. pipe entering the chimney flue from an adjoining A main object of my invention is to provide room. The damper 5 is a hollow bell-shaped such an automatic damper mounted for bodily member. As shown in Figure 3, a sleeve 50 closes vertical movement, and having its weight balthe upp end of the da p and s S idab e On 10 anced by spring means, so that the damper may the rod 6. This rod is secured in a bridged supbe responsive to even small pressure decreases p Which y e Se in the pp end within the chimney flue, of the inlet conduit I. The damper is suspended A further object is to provide means whereby upon a spring 5| connected to an arm 52, which the position of the damper may be adjusted so may include a thermostatic element. This arm 15 that it will open under the influence of. a selected eng ges in a slotted collar 53 to which the spr decrease in pressure within the chimney flue, 5| is directly attached. An adjusting screw 54 which may be smaller or greater than a given y be P ov to ove t damper p dOWIl decrease in pressure which will open the damper on the red 6 y deflecting the a when it i i th n r al o iti n, Cooperating with the damper is an outer mem- 20 Another object of my inv ti i t f r ber shown as an annular Venturi tube 8, which the damper member and its cooperating opening 010885 the Outer end of the inlet p pe The Openin such a manner thata Venturi-shaped aperture n in this Venturi tube decreases in area to a is produced when the damper is opened by a 19- minimum section 8 I which lS cylindrical in shape crease in flue pressure. This Venturi-shaped Over an pp ab length- The Opening a a n 5 aperture causes the incoming air to enter the diverges to the inner end f th tube. at chimney flue t a high v l it h opening When the damper is opposite the portion 8|, it formed may increase in area slightly at its inner may be considered as being in s d p siti end, so that while the high velocity is maintained The central damper member 5 fi snugly Withto a large extent, the air flow will be smoothed in the Cylindrical portion 3| 0f t Venturi tube, 30 out and any appreciable turbulence in the flow and its Section Of a m diameter is a y of the incoming air will be eliminated. adjacent the middle of the cylindrical section of t is 21150 an object of my invention t the Venturi tube. In this position of the parts a ciate with such dampers a thermostatic element ven eas in flue pressure will draw the so governed by the temperature of the room in damp r d wn below th d 8 f th V tu tube which the check draft damper is located, which a ainst th acti n of t sp in 5 a d a l w a thermostatic element operates to move the to flow into the chimney flue. The inner end of damper either side of a normal position, so that the da pe 5 ay decrease S t y in diameter, the damper will open under the influence of either as shown at 55, so that when the parts are in the 40 a greater or a smaller decrease in flue pressure dotted line position shown in Fi r an 4;!) than a given decrease, which given decrease will u ar Vent Ope W be formed y the open the damper when the parts are in the nor-- operating damper and Venturi tube, which openmal position. This thermostatic element may be ing first decreases in area to a minimum secsupplemental to the manual adjustment pretion, and then gradually increases again to the viously mentioned. 7 inner end of the parts. 45

Other objects of my invention, resulting more The adjusting screw 54 may be manipulated to particularly from the shape and disposition of move the parts to the dotted line position shown the parts, will appear in the following descripin Figure 3. The maximum diameter of the tion and claims, with reference to the accomdamper 5 will now be adjacent the upper end of panying drawing. the cylindrical portion ill of the Venturi tube. 50

Figure 1 is an elevation view of my device as With the parts in this position a decrease in flue installed in a flue pipe joining a furnace and a pressure greater than the given decrease required stack, parts of which are shown in section. to open the damper when it is midway of the Fi r 2 is a plan view Of. my device insta led cylindrical section 8| will be necessary to increase 55 in a P the air inlet opening, since the damper 5 will now 55 have to move a greater distance against the resisting action of the spring 5|. On the other hand, if the adjusting screw 54 is manipulated to lower the damper until its maximum diameter lies adjacent the lower end of the cylindrical section 8! only a smal decrease in flue pressure will be necessary to move the damper to the open position.

If the arm 52 is a thermostatic element, it will operate to the same end as the manual adjustment 54. A furnace room is often inclined to become overheated, and since it is sometimes desirable to store apples or other fruit in such a room I provide means whereby its temperature may be controlled to prevent spoiling of the stored fruit. Upon an increase in room temperature the arm 52 will bend to lower its free end, thus to move the damper 5 downward, which will then open under the influence of a smaller decrease in pressure within the chimney flue. A decrease in room temperature will conversely cause the thermostatic element to move the damper to a higher position, and a greater decrease in flue pressure will be required to open it. Thus, when the room becomes over-heated, the maximum diameter of the damper will lie adjacent the lower end of the cylindrical section 8|, and upon being opened by a small decrease in flue pressure, warm air will flow from the room through such opening, and cool air from the outside may replace .the warm air removed through the check draft damper to again cool the room temperature. Such operation will serve both to control the temperature of the room, and to simultaneously lessen the intensity of the fire in the furnace. A stop pin 9 is provided to prevent the damper from moving past the end of the rod 6 under the influence of a warm room effecting a downward movement of the damper and a large decrease in flue pressure, which further draws the damper downward. 1

It will also be noted that an increase in flue pressure would move the hollow bell-shaped damper 5 in an outward direction. When an oil burner is lighted, a miniature explosion sometimes occurs in the furnace, which tends to blow soot out through the chimney flue and through the furnace doors. With this installation any such sudden pressure increase will tend to force the damper 5 outward, and both the force and concussion of the burst will be absorbed in an oscillating and damping movement of the damper in the Venturi tube.

It will be seen that the delicate balance of my damper renders it sensitive to even a small increase in draft, when desired, and the intensity of a furnace fire and in addition room temperaturemay be very accurately controlled by its use without constant personal attention.

'It may be found desirable, in some installations, to ventilate or to regulate the temperature of spaces or rooms other than that in which the furnace is located or in which the smoke pipe 2 is found. In such instances the inlet pipe I may be extended from its connection with the smoke pipe into a distant room or even to a point out of doors, or its discharge end may be connected direct with the chimney flue instead of to the smoke pipe. In such instances the space or room to be ventilated will be the point where the air is admitted to the inlet pipe I, at which point will be found the damper 5 and the thermostatic element 52, if the latter is to be used, as it ordinarily would be.

What I claim as my invention is;

1. A check draft damper comprising an inlet conduit connected to the chimney flue and a member movable from a normal closed position, under the influence of a given decrease in pressure within the flue, toadmit air through said conduit from the surrounding room, and means responsive to increase in temperature of such room, operatively connected to effect movement of said movable member to a position wherein it is responsive toa lesser decrease in pressure.

2. A check draft damper comprising an inlet conduit connected to the chimney flue, a damper supported relative to the inlet opening for movement inward from a closed position, under the influence of a decrease in pressure within the conduit, and thermostatic means controlled by the temperature of the room in which the check draft damper is located, to displace the point of support of said damper relative to the dampers closed position.

3. A check draft damper comprising an inlet conduit connected to the chimney flue, an annular member in said conduit having an opening decreasing in diameter from its outer end to a section of minimum diameter and again increasing in diameter from such section to its inner end, and a cooperating central member increasing in diameter from its outer end to a section of maximum diameter, and again decreasing in diameter from such section to its inner end, the maximum diameter section of said central member lying adjacent the section of minimum diam eter of said annular member in the closed position of the parts, said central member being movable relative to said annular member to an open position under the influence of a given decrease in pressure within the flue.

4. The combination of claim 3, and adjusting means associated with one of said members adapted for adjustment to effect movement of the central member to open position under the influence of a decrease in pressure within the flue smaller than such given decrease and conversely adapted for adjustment to effect movement of the central member to open position only under the influence of a decrease in pressure within the flue greater than such given decrease.

5. The combination of claim 3, the section of minimum diameter of the annular member being of appreciable length, and adjusting means operable to position the maximum diameter section of the central member adjacent any desired portion of the minimum diameter section of the annular member, whereby the decrease in pressure necessary to move the central member to open position may be selected at will at a smaller or greater value than the given pressure decrease.

6. A check draft damper comprising an inlet conduit connected to the chimney flue, a member received in said conduit having an opening therein converging from its outer end to a cylindrical section and again diverging to its inner end, a cupped member received in the opening of said first member, its concave surface facing inward, and its convex surface diverging from its outer end to a maximum section normally disposed adjacent the cylindrical section of said first member, said second member being movable outward from such normal position relative to said first member under the influence of an increase in pressure within the flue, and movable inward from such normal position relative to said first member under the influence of a decrease in pressure within the flue.

7. A check draft damper comprising an air in! let pipe communicating with the chimney flue, a member extending inward from the end of said pipe having a circular aperture progressively decreasing in area inward from the pipe end, a cooperating circular member disposed within such aperture progressively increasing in area inward from the pipe end, the section of maximum area of said second member being normally disposed opposite the section of minimum opening in said first member, and the common axis of the two members being vertical, and spring means connected to the second member to balance the weight of such member, thus to maintain it in a position of minimum opening under normal conditions, but adapted to be moved bodily to a position of increased opening under the influence of a decrease in pressure within the chimney flue.

8. A check draft damper comprising an air inlet pipe communicating with the chimney flue, a support mounted thereon, a rod secured in said support coaxial with said inlet pipe and extending within the outer end thereof, a Venturi tube encircling said rod and closing the end of said pipe with the exception of the Venturi opening, the throat of said Venturi tube including a cylindrical section, a bell-shaped member slidable on said rod and adapted to fit snugly within the cylindrical section of the Venturi tube throat, the concave side of said member facing the chimney end of the pipe, a thermostatic element mounted on said support, its free end being adapted to move inward of said pipe upon an increase in temperature of the room, a spring interconnecting said thermostatic element and. said bell-shaped member to maintain the periphery thereof adjacent to the cylindrical section of the Venturi tube throat under normal conditions, but adapted to permit movement of said member inward of the inlet pipe upon a decrease in pressure within the chimney flue or outward upon an increase of pressure in the flue, and manual adjusting means to adjust the normal position of said bell-shaped member relative to said Venturi tube.

9. A check draft damper for use in an inlet conduit connected to a chimney flue, comprising a damper plate disposed within said inlet conduit, the latter including a restricted portion within which the damper plate is normally disposed, means supporting the damper plate for bodily rectilinear movement through such restricted portion, and means to impose an increasing resistance to such movement either side of such normal position.

10. A check draft damper for use in an inlet conduit connected to a chimney flue, comprising a damper element normally disposed within the inlet opening of such conduit, and means supporting the damper element for movement axially of the conduit to either side of such normal position, the damper element and the inlet opening being relatively disposed and shaped to increase the effective size of the aperture as movement progresses away from such normal position.

11. A damper for controlling an air inlet conduit, comprising a support, a rod supported thereby axially of the conduit, a damper plate slidably mounted on said rod, plate supporting means, and a spring interconnecting said plate and said means.

12. The combination of claim 11, and a thermostat responsive to room temperature associated with the plate supporting means to vary the position thereof.

13. The combination of claim 11, and manually operable means to adjust the plate supporting means.

14. A damper for controlling an air inlet conduit having a restricted portion intermediate its ends, and flaring oppositely therefrom, a damper plate of a size to pass through such restricted portion, a support, and a spring interconnecting said damper plate and said support, and supporting the damper plate normally in registry with the restricted portion, for movement under the influence of changes of pressure to either side thereof.

15. A damper for controlling an air inlet conduit having a restricted portion intermediate its ends, and flaring oppositely therefrom, a damper plate of a size to pass through such restricted portion, a thermostatic element, a spring form- L ing the sole support for said damper plate connected to said thermostatic element, and supporting the damper plate normally in registry with the restricted portion, for movement to either side thereof under the influence of changes in pressure, and changes in temperature affecting said thermostatic element.

16. A check draft damper, comprising an inlet conduit having a restricted portion, connected to a chimney flue, a damper member received in said conduit and of a size to pass readily through the restricted portion of said conduit, and means guiding the damper member for bodily rectilinear movement to one side of such restricted portion under the influence of a decrease in chimney flue pressure from atmospheric pressure, to increase the area of inlet opening, and for bodily rectilinear movement to the other side of such restricted portion under the influence of an increase in chimney flue pressure, to damp movement of air emerging from such inlet opening.

17. A check draft damper for controlling an air inlet into a chimney flue, comprising a damper member movable in an opening in such flue under the influence of draft fluctuations in the flue, and located within a room, and thermoresponsive means progressively responsive to changes in the temperature of air in such room, and operatively connected to control, progressively, said damper member in accordance with such temperature variations.

18. A check draft damper for controlling an air inlet into a chimney flue, comprising a damper member movable in an opening in such flue under the influence of draft fluctuations in the flue, and located within a room, and thermoresponsive means directly connected to said damper member to move it compensably in response to variations of the temperature of the air in such room.

CLARENCE B. ROGERS. 

